Encapsulated Drive for Single-Use Bioreactor Sterility
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Solution Overview
Problem
Coupling a generally unsterile drive to a sterile mixer shaft in single-use containers with flexible walls poses a challenge in maintaining sterility, as existing solutions like magnetic stirrers or mechanical couplings are not effective in preventing contaminant ingress.
Innovation Solution
A mixing system with an encapsulated drive made of plastic, which can be disposed of after use, featuring seals that prevent particle and contaminant ingress, allowing the drive to be situated either inside or outside the container, and using pneumatic or hydraulic drives that can be produced from plastic for environmentally friendly disposal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a magnetic stirrer or mechanical coupling is used to drive the mixer shaft, then the mixing function is achieved, but the sterility of the container interior is compromised due to contaminant ingress through the drive coupling
Solution Approach 1:
The system is divided into two separate parts: a sterile mixer shaft with mixing elements that remains inside the container, and a non-sterile drive unit that is encapsulated and disposed of separately. This segmentation allows the mixing function to be maintained while preventing contaminant ingress through the drive coupling, as the drive is isolated in an encapsulation that can be discarded with the container after use.
Solution Approach 2:
The drive unit is designed as a disposable component that is encapsulated in a sterile barrier and disposed of together with the single-use container after the experiment. This eliminates the need for complex sterilization of the drive mechanism itself, while maintaining sterility during use. The encapsulation acts as a disposable sterile barrier that prevents contaminant ingress during the experiment and is then discarded.
2Ease of operation
If a through-hole is created in the container wall to guide the mixer shaft, then mechanical coupling is achieved, but the complexity of sealing against contaminants increases
Solution Approach 1:
The drive mechanism is completely extracted from the sterile environment and placed in a separate encapsulated unit. This eliminates the need for complex sealing arrangements at the container wall, as the drive does not need to mechanically couple through the wall. The mixer shaft can be simply guided through the wall without requiring sealed connections to the drive mechanism.
Solution Approach 2:
The encapsulation acts as an intermediary barrier between the non-sterile drive and the sterile container interior. Instead of creating complex sealed connections through the container wall, the encapsulation provides a simple sterile barrier that allows the drive to be positioned outside while maintaining sterility inside the container.
3Reliability
If the drive is disposed of after use with the container, then sterility is maintained, but the device complexity increases due to encapsulation requirements
Solution Approach 1:
The encapsulation is implemented using flexible plastic materials that can be easily formed into protective barriers. This simplifies the encapsulation structure compared to rigid sealed enclosures, as the flexible plastic can conform to the drive shape and provide effective sealing without complex assembly. The flexible material allows for simple integration with the single-use container system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The encapsulated drive maintains sterility within the single-use container, preventing contamination and allowing for effective mixing while being easily disposable, suitable for sterile media and cell cultures.
Implementation Method 1
The outlet of the mixer shaft from the encapsulation is preferably sealed by a seal. In the process, seals made of plastic, preferably lip seals or molded-on multi-component injection-molded seals, are preferred. Such seals are impenetrable for gasses, liquids and microorganisms.
Implementation Method 2
the mixing element is for this purpose equipped with permanent magnets, which are driven by a rotating magnetic field
Implementation Method 3
vibration mixers, in which a perforated mixer plate is subjected to a linear up and down motion
Implementation Method 4
the motor was sterilized prior to installation by a treatment with electromagnetic radiation
Implementation Method 5
the motor was sterilized prior to installation by a treatment with electromagnetic radiation, by autoclaving
Data Source
AI summary
A mixing system has a single-use container (1) with flexible walls and a mixing device. The mixing device has at least one encapsulated drive (5) and a mixer shaft (3). The drive (5) can be disposed of after use together with the mixer shaft (3) and the single-use container (1). The mixing system can be used in biotechnology and the pharmaceutical industry for mixing liquids, dissolving solids or cultivating cells and microorganisms.